[3] He earned both bachelor's (1956)[4] and master's (1981)[4] in speech communication from Emerson College in Boston,[4] although his undergraduate education was interrupted due to his service for four years in the United States Air Force during the Korean War.

[3] He performed on Broadway in All in Good Time (1965)[1] and A Place Without Doors (1970-1971),[1] and a revival of The Little Foxes (1967–1968) as Horace Giddens, alongside Anne Bancroft.

[6] In 1979, Dysart portrayed a good-hearted physician treating a dying billionaire in the film Being There,[7] starring Peter Sellers and Melvyn Douglas.

In 1980, he played Abraham Lincoln's Secretary of War Edwin Stanton in the television film The Ordeal of Dr.

[7] He voiced the kindly miner Uncle Pom in the Disney English-language version of Hayao Miyazaki's 1986 adventure classic Castle in the Sky,[7] and the character of Cogliostro on Todd McFarlane's Spawn: The Animated Series, which aired on HBO.

[5] Dysart was nominated four years in a row for Primetime Emmy Award for Outstanding Supporting Actor in a Drama Series between 1989 and 1992,[5] for his role as Leland McKenzie on L.A. Law, winning in 1992.